Diffusion resistors or well resistors are commonly implemented as nwell structures in P− substrate twin-well bulk CMOS technology surrounded by an adjacent pwell. These diffusion resistors, however, suffer from relatively low breakdown voltage (BV) and high voltage coefficient of resistivity (VCR) by which conventional diffusion resistors are typically unsuitable for high voltage applications. Alternative resistor structures may be used, such as silicided polysilicon resistors or silicide blocked polysilicon resistors. Polysilicon has a relatively low sheet resistance and these resistor structures are therefore larger than corresponding diffusion resistors for a given desired resistance value. For instance, typical diffusions may have a resistivity of about 500 ohms per square, whereas polysilicon is about 20 ohms per square. For high resistance values, moreover, narrow polysilicon line widths are prone to process variations. In addition, silicide blocked poly resistors require an extra mask to block silicide, leading to higher manufacturing cost. Furthermore, polysilicon can only accommodate a certain amount of current density. Another alternative is use of lightly doped high-voltage nwell (HVNWELL) resistors, in which dopant concentration is lower than normal CMOS nwells, in some cases by a factor of 10. The lighter doping provides high breakdown voltage capabilities. However, the lighter well doping of HVNWELLs results in higher VCR than more heavily doped diffusion resistors. Accordingly, improved integrated circuits and fabrication techniques are needed for providing integral resistors.